The inventive subject matter relates to power supply apparatus and methods, more particularly, to wireless power transfer apparatus and methods.
Wireless power transfer is used in a variety of different applications, including battery charging for portable electronic devices, such as cell phones and handheld appliance (e.g., electric shavers and toothbrushes), and for higher-power applications, such as vehicle charging. Wireless power transfer techniques have also been employed to provide power to computing devices, such as servers.
FIG. 1 illustrates a DC/DC converter arrangement commonly used in conventional wireless power transfer systems. The system includes a transmitter circuit 10 configured to be coupled to a DC power source. The transmitter circuit 10 is a converter circuit including transistors Q1, Q2 and an output network including a capacitor Cr and inductors Lr, Lp. The transmitter circuit 10 is coupled to a primary winding of a transformer 20. A receiver circuit 20 is coupled to a secondary winding of the transformer 20 and includes another converter circuit including a rectifier comprising diodes D1, D2, which develops an output voltage Vo across and output capacitor Cf. FIG. 2 illustrates a conventional split core arrangement used for the transformer 20, including first and second separable coil assemblies 20a, 20b, including E-shaped magnetic cores 22a, 22b having first and second windings 24a, 24b on middle legs thereof. When providing wireless power transfer, the coil assemblies 20a, 20b are brought in close proximity to facilitate flux transfer between the cores 22a, 22b. Generally, efficiency of power transfer is dependent upon a distance d between the cores 22a, 22b. 